Brown Rat

Rattus norvegicus

Francach donn


Brown Rat

Is a rat just a bigger version of a mouse?

Not really, although rats and mice are in the same family of rodents. Rodents are one of the most successful mammal groups, accounting for 40% of mammal species! All rodents have strong sharp incisor teeth (front teeth) that grow throughout life,

meaning the animal must constantly gnaw at things to wear the teeth down. This gnawing habit, along with the fact that they carry many diseases, has made rats one of the most deeply

unpopular animals on the planet. However, the brown rat is also an intelligent and adaptable animal that plays a vital role in recycling the refuse left by wasteful humans.

Is the brown rat native to Ireland?

No, it only arrived in Ireland in the early 1700s! Despite the Irish name Francach, which means ‘from France’, brown rats probably originated in China, and moved westwards with trade and ships. Over time it gradually displaced the Black Rat (or ship rat),

Rattus rattus, which arrived here centuries earlier. The Black Rat carried the Black Death, bubonic plague. It is now rarely seen in Ireland except at Dublin port, but is still common in tropical countries.

Where do brown rats live?

They are common and widespread throughout Ireland, and

anywhere that humans are, you will find rats too. Much bigger than a mouse, the brown rat measures up to about 25cm excluding the long scaly tail, which is nearly as long as the body. The fur is grey-brown. And can be quite greasy. The ears are quite small and the eyes large, although hearing is better than sight. The senses of smell and touch are very important, so the rat has a large nose and long whiskers. Rats will make a home anywhere they can access food and cover, including farm buildings, under houses, rubbish dumps and even sewage systems.

Do brown rats live in groups?

Yes, rats are social animals and can live together at very high densities when food is plentiful. A group of rats is called a clan, which holds its own territory. Clans may fight for resources, although when there is plenty of food they are more tolerant of each other. Rats also spend a lot of time grooming each other, so diseases pass quickly between them.

What do brown rats eat?

Rats will eat almost anything. Like most rodents, their original food would have been grain and seeds, but they have adapted their diet to include anything they can gnaw on; stored grain and vegetables, leftover food, waste of all kinds, even the likes of chipboard and soap! They will also take animal prey like worms and insects. Their instinct for gnawing is so strong that they will also gnaw on things that have no food value, such as plastic and electrical wiring. And although all this makes them a pest, they are also much more valuable than many of us realise, because they get rid of so much waste.

What kills brown rats?

Rats are important prey for many other animals. Birds such as owls, kestrels, buzzards and kites all regularly hunt them.

Mammals that feed on rats include foxes, stoats, pine martens, mink, dogs and of course the domestic cat, which  has been a pest controller for humans for thousands of years.

How long do brown rats live?

Rats rarely live as long as two years; their life cycle relies on a high breeding rate rather than a long lifespan.

Do rats hibernate?

No. Rats have no need to hibernate because they usually have access to plenty of food & shelter.

Can rats climb?

Rats are exceptionally good climbers, although the ship rat, which is virtually extinct in Ireland, is marginally better than the brown rat.

Do brown rats make noises?

Yes, rats are quite vocal. As well as a number of audible squeaking and piping calls, they also produce ultrasound signals. These are usually not audible to the human ear, but can be heard on a bat detector if tuned into the right frequency.

When are baby rats born?

Brown rats have a very high birth rate, and can breed almost year-round. A rat is capable of breeding at the age of 3 months, and a female can have 3-5 litters of several babies (pups) a year. The young are born blind and naked safe in the nest, and are raised solely by their mother. They are weaned after just 22 days, and are then ready to disperse - but the mortality rate is very high.

Are brown rats protected?

Brown rats are not protected, so it is legal to trap them or poison them if they are causing damage to food stores or property, or likely to spread disease.

National Parks & Wildlife Service, 7 Ely Place, Dublin 2. Phone: +353 1 8882000 Fax: +353 1 8883272